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Plate XIX. Fig. 1 7, is another fossil from Shepey, the general 
structure of which agrees with the preceding, excepting that, in this 
body, there appears to have been two rows of hexagonal bodies. As, 
in the preceding figure, the masticating surface was shown ; so here 
the other surface, the bony base, is shown ; and this chiefly for the 
purpose of showing the perpendicular fibres, which, giving to this 
surface a brushlike appearance, induced Lhwydd to give the name of 
Scopula litoralis to this fossil. 
The comminuting surface of the first of these fossils, Plate XIX. 
Fig. 16, is gently convex ; whilst that of the latter, Fig. 1/b possesses a 
correspondent degree of concavity. From this circumstance I am led 
to suppose, that the former has been the lower part or tongue, and the 
latter the upper part or palate, of perhaps the same species of fish. 
Plate XIX. Fig. 14, is another fossil palate, of a different species. 
This differs from the preceding species not only in the form of its 
plates, but in its structure. The lateral substances are here plates, 
lying over each other, like the tiles of a roof, ready to succeed, as 
the upper plates are worn or broken away. The substance of the 
plates, in this specimen, when examined by a lens, are seen to be 
very different from that of bone ; appearing, indeed, rather deserving 
a place between enamel and horn : possessing, with a denseness of 
structure like that of the former substance, a small degree of the 
transparency observable in the latter. 
Those bodies which are called by the quarrymen petrified leeches, 
of which one is figured Plate XIX. Fig. 15, and which are frequently 
found in the lime-stone of Wiltshire and of Oxfordshire, were termed 
by Da Costa Palatum Umax, or the slug-palate. These bodies are of 
an oblong figure, and generally a little pointed towards their ends. 
Their colour is of a dark brown, and they frequently possess a tolerable 
polish. On their upper surface are innumerable fine and slightly un- 
dulating rugae, which commence at the sides, and sometimes unite in 
a fine irregular line, which passes longitudinally along the middle of 
